426 
On the Continuous Growth of Wheat on the 
peas, wheat, and oats, the last four crops being grown without 
any manure whatever. In the event of a failure of the clover- 
crop, such a course would not at the period have been unusual 
in the district, although in those days a top-dressing of soot 
would, in all probability, have been applied to the wheat. In 
this case, however, it was not applied ; and, even if it had been 
applied, the land after the oat-crop would be considered, agri- 
culturally speaking, to be exhausted. 
It was at this period that the Rothamsted experiments were 
commenced, for the purpose of ascertaining what amount of 
crop the land would yield in wheat, without the aid of manure. 
The cultivation has been throughout of the most simple descrip- 
tion, and no attempt has been made to increase the crop by 
deep, or subsoil ploughing. The land has, however, been kept 
free from weeds. 
In the following table will be found a summary of the results 
given in 4 periods of 10 years each : — 
Table XXII. — Showing the NriUBER of Bushels of Deessed Corn 
per Acre, the "Weight per Bushel, and Total Produce of Corn 
and Straw of the Permanently Unmanured Land, in Average 
Periods of Ten Years. 
Bushels of 
Dressed 
Corn per 
Acre. 
Weight per 
Bushel. 
ToUl Produce 
Corn and 
Straw in lbs. 
Mean of 10 years, 1844-1853 
Mean of 10 years, 1854-1863 
Mean of 10 years, 1864-1873 
Mean of 10 years, 1874-1883 
15| 
16J 
12i 
101 
58-25 
57- 57 
58- 97 
58-25 
2711 
2728 
1924 
1614 
14 
58-26 
2244 
We have already noticed the number of fine wheat seasons 
which occurred during the second 10 years of the experiment, and 
we may further mention that the effect of these favourable seasons 
was sufficient to make the yield of grain of the second 10 years 
of unmanured wheat slightly higher than that of the first period, 
the average of the dressed corn per acre in the first period being 
15|, and in the second period 16J bushels per acre. The total 
produce (corn and straw), which is a much more accurate measure 
of the available fertility of a soil than the grain alone, shows a 
considerable reduction in the second period as compared with 
the first. 
In the third period of 10 years, the average decline is very 
decided, the mean for the 10 years being not quite 13 bushels 
